Probable cause is defined as the reasonable belief that a person has committed a crime. To determine probable cause, a test is used to determine if probable cause exists and is sufficient enough to arrest a suspect. The test must show that the facts and circumstances of the officer's knowledge are sufficient enough to warrant a reasonable person to believe a suspect has committed, is committing, or is about to commit a crime.

Item Seizure

When items related to a crime must be seized, the presence of reasonable cause must exist in order to take any contraband, stolen property, or items that would aid in proving a crime has been committed. The arresting officer is expected to assess the situation and their findings show a reasonable person would see the evidence as valid.

The Fourth Amendment

The Fourth Amendment prohibits an officer from making an arrest without showing probable cause. In Lamb, 738 F.2d 1005, 1007 (9th Cir. 1984), probable cause is shown to exist when "the facts and circumstances within the arresting officer's knowledge are sufficient to warrant a prudent person to believe that a suspect has committed, is committing, or is about to commit a crime." If probable cause is used without justification, a case can be made in both civil and criminal charges.

Probable cause is presumed to exist until the contrary is proven, even if the suspect is accused through malicious intent. Any grounds for suspicion that a crime or misdemeanor has been committed, must be investigated for the purpose of public justice and for the good of the community as a whole.